Multi-speed transmission having three planetary gear sets

ABSTRACT

A transmission is provided having an input member, an output member, three planetary gear sets, a plurality of coupling members and a plurality of torque transmitting devices. Each of the planetary gear sets includes first, second and third members. The torque transmitting devices include clutches and brakes.

FIELD

The invention relates generally to a multiple speed transmission having a plurality of planetary gear sets and a plurality of torque transmitting devices and more particularly to a transmission having eight or more speeds, three planetary gear sets and a plurality of torque transmitting devices.

BACKGROUND

The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.

A typical multiple speed transmission uses a combination of friction clutches, planetary gear arrangements and fixed interconnections to achieve a plurality of gear ratios. The number and physical arrangement of the planetary gear sets, generally, are dictated by packaging, cost and desired speed ratios.

While current transmissions achieve their intended purpose, the need for new and improved transmission configurations which exhibit improved performance, especially from the standpoints of efficiency, responsiveness and smoothness and improved packaging, primarily reduced size and weight, is essentially constant. Accordingly, there is a need for an improved, cost-effective, compact multiple speed transmission.

SUMMARY

A transmission is provided having an input member, an output member, three planetary gear sets, a plurality of coupling members and a plurality of torque transmitting devices. Each of the planetary gear sets includes first, second and third members. The torque transmitting devices are for example clutches and brakes.

In another embodiment of the transmission, the transmission has an input member, an output member, first, second, and third planetary gear sets. Each of the planetary gear sets has a sun gear, carrier and ring gear members. The input member is continuously interconnected to the sun gear member of the second planetary gear set and the output member is continuously interconnected to the ring gear member of the third planetary gear set and the carrier member of the first planetary gear set.

Moreover, a first interconnecting member continuously interconnects the ring gear member of the first planetary gear set with the carrier member of the second planetary gear set. A second interconnecting member continuously interconnects the carrier member of the first planetary gear set with the ring gear member of the third planetary gear set. A third interconnecting member continuously interconnects the ring gear member of the second planetary gear set with the carrier member of the third planetary gear set

Additionally, a first torque transmitting mechanism is selectively engageable to interconnect the sun gear member of the second planetary gear set and the input member with the sun gear member of the third planetary gear set. A second torque transmitting mechanism is selectively engageable to interconnect the sun gear member of the second planetary gear set and the input member with the ring gear member of the second planetary gear set and the carrier member of the third planetary gear set. A third torque transmitting mechanism is selectively engageable to interconnect the sun gear member of the second planetary gear set and the input member with the sun gear member of the first planetary gear set. A fourth torque transmitting mechanism is selectively engageable to interconnect the ring gear member of the second planetary gear set and the carrier member of the third planetary gear set with the stationary member. A fifth torque transmitting mechanism is selectively engageable to interconnect the sun gear member of the third planetary gear set with the stationary member. A sixth torque transmitting mechanism is selectively engageable to interconnect the sun gear member of the first planetary gear set with the stationary member. The torque transmitting mechanisms are selectively engageable in combinations of at least two to establish at least eight forward speed ratios and at least one reverse speed ratio between the input member and the output member.

Thus, it is an object of the present invention to provide a transmission having at least eight forward speeds and at least one reverse.

It is further an object of the present invention to provide a transmission having three planetary gear sets, a plurality of coupling members and a plurality of torque transmitting devices.

Further objects, aspects and advantages of the present invention will become apparent by reference to the following description and appended drawings wherein like reference numbers refer to the same component, element or feature.

DRAWINGS

The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

FIG. 1 is a lever diagram of an embodiment of a eight speed transmission according to the present invention;

FIG. 2 is a diagrammatic illustration of an embodiment of a eight speed transmission according to the present invention; and

FIG. 3 is a truth table presenting the state of engagement of the various torque transmitting elements in each of the available forward and reverse speeds or gear ratios of the transmission illustrated in FIGS. 1 and 2.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.

At the outset, it should be appreciated that the embodiments of the eight speed automatic transmission of the present invention have an arrangement of permanent mechanical connections between the elements of the three planetary gear sets. A first component or element of a first planetary gear set is permanently coupled to a second component or element of the second planetary gear set. A second component or element of the first planetary gear set is permanently coupled to a third component or element of the third planetary gear set. A third component or element of the second planetary gear set is permanently coupled to a second component or element of the third planetary gear set.

Referring now to FIG. 1, an embodiment of an eight speed transmission 10 is illustrated in a lever diagram format. A lever diagram is a schematic representation of the components of a mechanical device such as an automatic transmission. Each individual lever represents a planetary gear set wherein the three basic mechanical components of the planetary gear are each represented by a node. Therefore, a single lever contains three nodes: one for the sun gear, one for the planet gear carrier, and one for the ring gear. The relative length between the nodes of each lever can be used to represent the ring-to-sun ratio of each respective gear set. These lever ratios, in turn, are used to vary the gear ratios of the transmission in order to achieve an appropriate ratios and ratio progression. Mechanical couplings or interconnections between the nodes of the various planetary gear sets are illustrated by thin, horizontal lines and torque transmitting devices such as clutches and brakes are presented as interleaved fingers. Further explanation of the format, purpose and use of lever diagrams can be found in SAE Paper 810102, “The Lever Analogy: A New Tool in Transmission Analysis” by Benford and Leising which is hereby fully incorporated by reference.

The transmission 10 includes an input shaft or member 12, a first planetary gear set 14 having three nodes: a first node 14A, a second node 14B and a third node 14C, a second planetary gear set 16 having three nodes: a first node 16A, a second node 16B and a third node 16C and a third planetary gear set 18 having three nodes: a first node 18A, a second node 18B and an output shaft or member 22.

The input member 12 is continuously coupled to the first node 16A of the second planetary gear set 16. The output member 22 is coupled to the second node 14B of the first planetary gear set 14. The first node 14A of the first planetary gear set 14 is coupled to the second node 16B of the second planetary gear set 16. The second node 14B of the first planetary gear set 14 is coupled to the third node 18C of the third planetary gear set 18. The third node 16C of the second planetary gear set 16 is coupled to the second node 18B of the third planetary gear set 18.

A first clutch 26 selectively connects the first node 16A of the second planetary gear set 16 and the input member or shaft 12 with the first node 18A of the third planetary gear set 18. A second clutch 28 selectively connects the first node 16A of the second planetary gear set 16 and the input member or shaft 12 with the second node 18B of the third planetary gear set 18. A third clutch 30 selectively connects the first node 16A of the second planetary gear set 16 and the input member or shaft 12 with the third node 14C of the first planetary gear set 14. A first brake 32 selectively connects third node 16C of the second planetary gear set 16 and the second node 18B of the third planetary gear set 18 with a stationary member or transmission housing 50. A second brake 34 selectively connects the first node 18A of the third planetary gear set 18 to a stationary member or transmission housing 50. A third brake 36 selectively connects the third node 14C of the first planetary gear set 14 to a stationary member or transmission housing 50.

Referring now to FIG. 2, a stick diagram presents a schematic layout of the embodiment of the eight speed transmission 10 according to the present invention. In FIG. 2, the numbering from the lever diagram of FIG. 1 is carried over. The clutches and couplings are correspondingly presented whereas the nodes of the planetary gear sets now appear as components of planetary gear sets such as sun gears, ring gears, planet gears and planet gear carriers.

For example, the planetary gear set 14 includes a sun gear member 14C, a ring gear member 14A and a planet gear carrier member 14B that rotatably supports a set of planet gears 14D (only one of which is shown). The sun gear member 14C is connected for common rotation with a first shaft or interconnecting member 42. The ring gear member 14A is connected for common rotation with a second shaft or interconnecting member 44. The planet carrier member 14B is connected for common rotation with the output member or shaft 22. The planet gears 14D are each configured to intermesh with both the sun gear member 14C and the ring gear member 14A.

The planetary gear set 16 includes a sun gear member 16A, a ring gear member 16C and a planet gear carrier member 16B that rotatably supports a set of planet gears 16D (only one of which is shown). The sun gear member 16A is connected for common rotation with the input member or shaft. The ring gear member 16C is connected for common rotation with a third shaft or interconnecting member 46. The planet carrier member 16B is connected for common rotation with the second shaft or interconnecting member 44. The planet gears 16D are each configured to intermesh with both the sun gear member 16A and the ring gear member 16C.

The planetary gear set 18 includes a sun gear member 18A, a ring gear member 18C and a planet gear carrier member 18B that rotatably supports a set of planet gears 18D (only one of which is shown). The sun gear member 18A is connected for common rotation with a fourth shaft or interconnecting member 48. The ring gear member 18C is connected for common rotation with output member or shaft 22. The planet carrier member 18B is connected for common rotation with the third shaft or interconnecting member 46 and a fifth shaft or interconnecting member 52. The planet gears 18D are each configured to intermesh with both the sun gear member 18A and the ring gear member 18C.

The input shaft or member 12 is continuously connected to an engine (not shown) or to a turbine of a torque converter (not shown). The output shaft or member 22 is continuously connected with the final drive unit or transfer case (not shown).

The torque-transmitting mechanisms or clutches 26, 28, 30 and brakes 32, 34 and 36 allow for selective interconnection of the shafts or interconnecting members, members of the planetary gear sets and the housing. For example, the first clutch 26 is selectively engageable to connect the input shaft or member 12 with the fourth shaft or interconnecting member 48. The second clutch 28 is selectively engageable to connect the input shaft or member 12 with the third shaft or interconnecting member 46. The third clutch 30 is selectively engageable to connect the input shaft or member 12 with the first shaft or interconnecting member 42. The first brake 32 is selectively engageable to connect the fifth shaft or interconnecting member 52 with the stationary element or the transmission housing 50 in order to restrict the member 52 from rotating relative to the transmission housing 50. The second brake 34 is selectively engageable to connect the fourth shaft or interconnecting member 48 with the stationary element or the transmission housing 50 in order to restrict the member 48 from rotating relative to the transmission housing 50. The third brake 36 is selectively engageable to connect the first shaft or interconnecting member 42 with the stationary element or the transmission housing 50 in order to restrict the member 42 from rotating relative to the transmission housing 50.

Referring now to FIG. 2 and FIG. 3, the operation of the embodiment of the eight speed transmission 10 will be described. It will be appreciated that transmission 10 is capable of transmitting torque from the input shaft or member 12 to the output shaft or member 22 in at least eight forward speed or torque ratios and at least one reverse speed or torque ratio with triple overdrive. Each forward and reverse speed or torque ratio is attained by engagement of one or more of the torque-transmitting mechanisms (i.e. first clutch 26, second clutch 28, third clutch 30, first brake 32, second brake 34 and third brake 36), as will be explained below. FIG. 3 is a truth table presenting the various combinations of torque-transmitting mechanisms that are activated or engaged to achieve the various gear states. An “X” in the box means that the particular clutch or brake is engaged to achieve the desired gear state. An “O” represents that the particular torque transmitting device (i.e. a brake or clutch) is on or active, but not carrying torque. Actual numerical gear ratios of the various gear states are also presented although it should be appreciated that these numerical values are exemplary only and that they may be adjusted over significant ranges to accommodate various applications and operational criteria of the transmission 10. An example of the gear ratios that may be obtained using the embodiments of the present invention are also shown in FIG. 3. Of course, other gear ratios are achievable depending on the gear diameter, gear teeth count and gear configuration selected.

To establish a reverse gear, the first clutch 26 and first brake 32 are engaged or activated. The first clutch 26 connects the input shaft or member 12 with the fourth shaft or interconnecting member 48. The first brake 32 connects the fifth shaft or interconnecting member 52 with the stationary element or the transmission housing 50 in order to restrict the member 52 from rotating relative to the transmission housing 50. Likewise, the eight forward ratios are achieved through different combinations of clutch and brake engagement, as shown in FIG. 3.

It will be appreciated that the foregoing explanation of operation and gear states of the eight speed transmission 10 assumes, first of all, that all the clutches not specifically referenced in a given gear state are inactive or disengaged and, second of all, that during gear shifts, i.e., changes of gear state, between at least adjacent gear states, a clutch engaged or activated in both gear states will remain engaged or activated.

The transmission of the present invention has many advantages and benefits over the prior art, for example, transmission 10 provides double transition shifts for speeds three to four, four to five and five to six. Further, the three to five and the four to six speed shifts are single transition skip shifts. Moreover, the present invention contemplates that transmission 10 may be configured for both front wheel and rear wheel drive vehicles.

The description of the invention is merely exemplary in nature and variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention. 

1. A transmission comprising: an input member; an output member; first, second and third planetary gear sets each having first, second and third members; a first interconnecting member continuously interconnecting the first member of the first planetary gear set with the second member of the second planetary gear set; a second interconnecting member continuously interconnecting the second member of the first planetary gear set with the third member of the third planetary gear set; a third interconnecting member continuously interconnecting the third member of the second planetary gear set with the second member of the third planetary gear set; and six torque transmitting mechanisms each selectively engageable to interconnect one of the first, second, and third members with another of the first, second, third members, and a stationary member, wherein a first of the six torque transmitting mechanisms is selectively engageable to directly connect the first member of the second planetary gear set and the input member with the first member of the third planetary gear set, and wherein a second of the six torque transmitting mechanisms is selectively engageable to interconnect the first member of the second planetary gear set and the input member with the third member of the second planetary gear set and the second member of the third planetary gear set, and wherein the torque transmitting mechanisms are selectively engageable in combinations of at least two to establish at least eight forward speed ratios and at least one reverse speed ratio between the input member and the output member.
 2. The transmission of claim 1 wherein the third member of the first planetary gear set, the first member of the second planetary gear set and the first member of the third planetary gear set are sun gears, the second members of the first, second and third planetary gear sets are carrier members and the first member of the first planetary gear set, the third member of the second planetary gear set and the third member of the third planetary gear set are ring gears.
 3. The transmission of claim 1 wherein three of the torque transmitting mechanisms are brakes each for connecting a plurality of the first, second, and third members to the stationary member and three of the torque transmitting mechanisms are clutches each for connecting a set of the first, second, and third members to another set of the first, second and third members.
 4. The transmission of claim 1 wherein a third of six torque transmitting mechanisms is selectively engageable to interconnect the first member of the second planetary gear set and the input member with the third member of the first planetary gear set.
 5. The transmission of claim 4 wherein a fourth of the six torque transmitting mechanisms is selectively engageable to interconnect the third member of the second planetary gear set and the second member of the third planetary gear set with the stationary member.
 6. The transmission of claim 5 wherein a fifth of the six torque transmitting mechanisms is selectively engageable to interconnect the first member of the third planetary gear set with the stationary member.
 7. The transmission of claim 6 wherein a sixth of the six torque transmitting mechanisms is selectively engageable to interconnect the third member of the first planetary gear set with the stationary member.
 8. A transmission comprising: an input member; an output member; first, second and third planetary gear sets each having first, second and third members, wherein the input member is continuously interconnected to the first member of the second planetary gear set and the output member is continuously interconnected to the third member of the third planetary gear set and the second member of the first planetary gear set; a first interconnecting member continuously interconnecting the first member of the first planetary gear set with the second member of the second planetary gear set; a second interconnecting member continuously interconnecting the second member of the first planetary gear set with the third member of the third planetary gear set; a third interconnecting member continuously interconnecting the third member of the second planetary gear set with the second member of the third planetary gear set; a first torque transmitting mechanism selectively engageable to interconnect the first member of the second planetary gear set and the input member with the first member of the third planetary gear set; a second torque transmitting mechanism selectively engageable to interconnect the first member of the second planetary gear set and the input member with the third member of the second planetary gear set and the second member of the third planetary gear set; a third torque transmitting mechanism selectively engageable to interconnect the first member of the second planetary gear set and the input member with the third member of the first planetary gear set; a fourth torque transmitting mechanism selectively engageable to interconnect the third member of the second planetary gear set and the second member of the third planetary gear set with the stationary member; a fifth torque transmitting mechanism selectively engageable to interconnect the first member of the third planetary gear set with the stationary member; and a sixth torque transmitting mechanism selectively engageable to interconnect the third member of the first planetary gear set with the stationary member, wherein the torque transmitting mechanisms are selectively engageable in combinations of at least two to establish at least eight forward speed ratios and at least one reverse speed ratio between the input member and the output member.
 9. The transmission of claim 8 wherein the third member of the first planetary gear set, the first member of the second planetary gear set and the first member of the third planetary gear set are sun gears, the second members of the first, second and third planetary gear sets are carrier members and the first member of the first planetary gear set, the third member of the second planetary gear set and the third member of the third planetary gear set are ring gears.
 10. A transmission comprising: an input member; an output member; first, second, and third planetary gear sets each having sun gear, carrier and ring gear members, wherein the input member is continuously interconnected to the sun gear member of the second planetary gear set and the output member is continuously interconnected to the ring gear member of the third planetary gear set and the carrier member of the first planetary gear set; a first interconnecting member continuously interconnecting the ring gear member of the first planetary gear set with the carrier member of the second planetary gear set; a second interconnecting member continuously interconnecting the carrier member of the first planetary gear set with the ring gear member of the third planetary gear set; a third interconnecting member continuously interconnecting the ring gear member of the second planetary gear set with the carrier member of the third planetary gear set; a first torque transmitting mechanism selectively engageable to interconnect the sun gear member of the second planetary gear set and the input member with the sun gear member of the third planetary gear set; a second torque transmitting mechanism selectively engageable to interconnect the sun gear member of the second planetary gear set and the input member with the ring gear member of the second planetary gear set and the carrier member of the third planetary gear set; a third torque transmitting mechanism selectively engageable to interconnect the sun gear member of the second planetary gear set and the input member with the sun gear member of the first planetary gear set; a fourth torque transmitting mechanism selectively engageable to interconnect the ring gear member of the second planetary gear set and the carrier member of the third planetary gear set with the stationary member; a fifth torque transmitting mechanism selectively engageable to interconnect the sun gear member of the third planetary gear set with the stationary member; and a sixth torque transmitting mechanism selectively engageable to interconnect the sun gear member of the first planetary gear set with the stationary member, and wherein the torque transmitting mechanisms are selectively engageable in combinations of at least two to establish at least eight forward speed ratios and at least one reverse speed ratio between the input member and the output member. 